Sealing porous formations



United States Patent p 2,858,892 SEALING POROUS FORMATIONS Paul G. Carpenter, Bartlesville, kla., assignor to Phillips Petroleum Company, a corporation of Delaware No Drawing. ()riginal application October 25, 1949, Serial No. 123,540, now Patent No. 2,735,269, dated February 21, 1956. Divided and this application July 5, 1955, Serial No. 520,115

11 Claims. (Cl. 166-29) This invention relates to sealing of porous or permeable formations. In one of its aspects it relates to scaling of Well formations. In another of its aspects the invention relates to scaling, plugging or partially plugging, of at least a part of a ground or earth formation so located that time is required to supply the sealing material to the precise location of the porous formation. In still another of its aspects the invention relates to a porous formation sealing method which is flexible and can be varied to adapt it to the sealing of formations located at various depths and composed of different substances, as will appear below. Other aspects and applications of the invention are apparent from this disclosure and its appended claims.

Methods for sealing porous formations have been proposed and are known in the art. These methods depend upon the use of morethan one material and these must be contacted within the formations to be sealed. This involves rather hit or miss methods of injection, particularly when the formation is waterbearing and the materials injected are not aqueous in character so that these do not readily wet the formation.

This application is a division of my copending application, Serial Number 123,540, filed October 25, 1949, now Patent 2,735,269, issued February 21, 1956.

This invention provides an entirely novel and highly advantageous method for sealing porous formations which constitutes an improvement in the art in that only one material is handled or manipulated and, therefore, all the required constituents or materials to lay down the sealing material are, per force, in contact at all parts of the formation.

According to the invention a water solution of a salt, of a water-insoluble acid, and a substance which upon gradual hydrolysis yields a free acid are injected into a porous formation before substantial hydrolysis of said substances can occur. In the formation, the hydrolysis occurs liberating the free acid which then reacts to form a water-insoluble free acid from said salt. The rate of liberation of the free acid by hydrolysis can be controlled by the addition of a buffer solution in an appropriate quantity to the solution being injected. Thus, because the buffer solution must first be used up before the pH becomes low enough to precipitate the free acid, the formation of the water-insoluble acid can be accelerated or controlled in respect of time depending upon the quantity of bulfer solution used.

The water soluble salts of water-insoluble acids which are adaptable for use in the method of this invention are numerous and can, in each case, be selected by mere routine test. Likewise, the water-soluble substances which will hydrolyze at a rate suitable for this use in the method of the invention also can be determined by mere routine test. In cases of too slow hydrolysis the feature of the invention of control by adding a buffer solution is to be borne in mind. Thus, a too slowly hydrolyzing substance, by itself unsuitable, may be made suitable by using a suitable buffer solution. More specifically, among the water-soluble salts of water-insoluble acids which can be used are rosin soaps, including abietic acid, metal salts of acidic materials derived from rosin, alkali metal and ammonium salts of polyacrylic acid, alkali metal naphthenates, salts of .carboxylic acids obtained by the oxidation of coal if the acids are insoluble at formation temperatures and the salts soluble at formation temperatures, salts of phthalic acid and salts of benzoic acid. As the hydrolyzing free acid liberating substance there can be used methyl foimate, ethyl acetate, methyl acetate, methyl glycolate, trimethyl cit-rate, dimethyl tartrate and acid anhydrides such as phthalic anhydride.

As a feature of the invention, and as a modification thereof, a Water solution of a salt of a water-insolubleacid, and an organic material, which will react with an oxidizing agent to yield an acid, and an oxidizing agent are injected into a porous formation. The rate of oxidation controls the rate of acid formation which in turn will control the rate at which the water-soluble salt of the water-insoluble acid will liberate said insoluble acid.

The water-soluble salts which have been mentioned above are also suitable for use in the modification of the invention just described. As the oxidizing agents there can be used potassium persulfate, sodium perchlorate, hydrogen peroxide, and sodium bromate. As the oxidizable organic material there can be used formaldehyde, acrolein, glyceraldehyde, crotonaldehyde, acetaldehyde, propionaldehyde, para-aldehyde, glucose and other reducing sugars, Water soluble ethyl-, propyl-, methyl-, butyl-mercaptans, and certain reducible inorganic materials such as sodium thiosulfate.

The invention provide superior methods for the sealing of porous or permeable formations in the sense that homogenous solutions or materials can be injected into the formations, there to lay down an insoluble sealing material. An important advantage of the invention is that the sealing materials can be removed, when desired, by dissolution using alkaline solutions.

From the foregoing it is also noted that the methods set forth use Water solutions which will easily and readily wet Water bearing formations.

Finally, the flexibility of the method is of great importance in its successful application to differently located formations. Thus, by the adjustment of the quantity of buffer used in the first embodiment of the invention, or by the proportioning of the oxidizing and of the oxidized compounds in the modification disclosed, any delay. necessary to lay down properly a sealing material in a porous formation can be accomplished. Thus even solid materials can be employed provided these materials will be dissolved before entering the formation or in time to be useful for the intended purposes.

Example I A ten percent water solution of sodium salt of rosin, a commercial product called Dresinate X and sold by Hercules Powder Company, is mixed together with methyl formate in a quantity to insure hydrolysis to sufficient formic acid to cause formation of rosin. At the end of several hours, water insoluble rosin has been formed. The time lapse of this reaction can be controlled to allow for pumping the admixed materials into, say, an oil well or a water injection well.

Example II Ten milliliters of a ten percent water solution of sodium salt of rosin, five milliliters of a ten percent water solution of glucose and five milliliters of a saturated solution of potassium persulfate were admixed and allowed to stand. Another admixture identically prepared was heated to C. and allowed to cool. After three hours the first solution was clear. The second solution was then opaque and contained precipitated rosin. After two and one-half days both solutions were quite opaque, indicating that the formation of insoluble rosin could be delayed for a time suflicient to allow the admixture to be injected into a well or other place to seal a formation.

3 Example III In the tabulation below are summarized seven tests conducted according to the invention showing the use of a buffer solution in varying quantities to vary the time alkyl esters of carboxylic acids, and a buffer, causing, by means of said buffer, said latter mentioned acid to be liberated at a retarded rate, whereby the solution is placed within the formation to be sealed and thereafter said taken to form the desired precipitate of sealing material. latter-mentioned acid liberates said insoluble acid, which Each test solution was shaken and allowed to stand at deposits in said formation, thus sealing same. room temperature (70-75 R). 7. The method of sealing a water-bearing, porous for- Standard Na Methyl hos- Shaken Precipitated Next Hours for Test Resinate, Acetate, phate pH at Day Preeipitate milliliters milliliters 10 butter, to Form milliliters 0 0 2:30 p. 20 5 0 231 p. 21 20 5 1 2:32 22 20 5 2 2133 p. 19% 20 5 3 2:34 p. m 9=00 a. m 18 5 20 5 4 2:35 p. m.. before 8:00 a. m. 17 5 20 5 5 2:36 p. m before 8:00 a. m 17% Buffers having an upper pH of about 8 or higher can be used according to the invention. Buffers of this kind are boric acid together with sodium hydroxide, sodium bicarbonate together with sodium carbonate, boric acid together with borax and borax alone.

Variation and modification are possible within the scope of the appended claims to the invention, the essence of which is that methods for sealing formations have been set forth comprising the use and ultimate admixture of an aqueous solution of a compound of a water-insoluble acid and a material which will slowly act to yield a free acid, which methods possess the inherent advantages set out and described herein constituting an improvement in the art. Equivalents within the scope of this disclosure and the appended claims can be readily determined by mere routine test and are intended to be included in said claims.

I claim:

1. The method of sealing a water-bearing, porous formation which comprises introducing into said formation in an amount suflicient to contact all parts of the formation to be sealed, a mixture consisting essentially of an aqueous solution of a water-soluble salt of a water-insoluble organic acid and a material which hydrolyzes to yield a free acid selected from the group consisting of water-insoluble anhydrides and water-soluble alkyl esters of carboxylic acids.

2. The method of claim 1 wherein a buffer is used to control the rate of liberation of free acid from said material by hydrolysis.

3. The method of sealing a water-bearing, porous formation which comprises introducing into said formation in an amount sufficient to contact all parts of the formation to be sealed, a mixture consisting essentially of an aqueous solution of a sodium rosin soap and methyl- .chloroacetate.

4. The method of sealing a water-bearing, porous formation which comprises introducing into said formation in an amount sufiicient to contact all parts of the formation to be sealed, a mixture consisting essentially of an aqueous solution of a sodium rosin soap and methylformate.

5. The method of sealing a water-bearing, porous formation which comprises introducing into said formation in an amount suflicient to contact all parts of the formation to be sealed, a mixture consisting essentially of an aqueous solution of a sodium rosin soap, methylacetate, and a buffer solution. mation which comprises introducing into said formation in an amount sufficient to contact all parts of the forma- 6. The method of sealing a water-bearing, porous fortion to be sealed, a mixture consisting essentially of a water solution of a water-soluble salt of a Water-insoluble organic acid, a material which slowly hydrolyzes when added to Water to liberate an acid selected from the group consisting of water-soluble anhydrides and water-soluble sodium resinate to mation which comprises introducing into said formation 25 sufficient phosphate buffer that the initial pH of said solution is not greater than 10, thus to permit the said solution to be placed within the formation to be sealed before liberation of rosin acid occurs, so that acetic acid liberated by hydrolysis of the methyl acetate reacts with said precipitate said rosin acid in said formation.

8. The method of sealing a water-bearing porous formation in a well with a material consisting essentially of a water-insoluble organic acid which comprises pumping into said well, in an amount sufficient to contact substantially all parts of the formation to be sealed, a material consisting essentially of a mixture of an aqueous solution of a water-soluble salt of a water-insoluble organic acid anda material selected from the group consisting of a water-soluble acid anhydride and a water-soluble alkyl ester of carboxylic acid, in an amount to insure hydrolysis to suflicient acid' to form water-insoluble organic acid from said water-soluble salt; maintaining said mixture in said porous formation for a time suflicient to lay down water-insoluble organic acid within the pores of the formation and thereby seal said formation.

9. The method of claim 8 wherein said mixture consists essentially of an aqueous solution of a sodium rosin soap and methylchloroacetate.

10. The method of claim 8 wherein said mixture consists essentially of an aqueous solution of a sodium rosin soap and methylformate.

11. In the process of sealing a porous, water-bearing formation in a well which comprises pumping into said well and into said formation, so as to contact substantially all parts of the porous formation to be sealed, a fluid which will form a solid within said formation and mantaining said fluid in said formation until a solid is formed therein, the improvement which comprises pumping into said formation a mixture consisting essentially of an aqueous solution of about 10 weight percent of a sodium rosin soap and at least about 5 volume percent of said aqueous solution of methyl acetate; and maintaining said mixture in contact with substantially all of the porous formation to be sealed until hydrolysis of said methyl acetate causes formation of solid water-insoluble rosin in the pores of the porous formation.

References Cited in the file of this patent UNITED STATES PATENTS 2,201,459 Van Hulst May 21, 1940 2,208,766 Lawton July 23, 1940 2,378,235 Miles June 12, 1945 2,676,152 Fortress et al Apr. 20, 1954 2,708,974 Fisher et al May 24, 1955 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION November A, 1958 Patent No. 2,858,892

Paul G. Carpenter s in the-printed specification It is hereby certified that error appear tion and that the said Letters of the above numbered patent requiring correc Patent should read as corrected below.

ine 27, for "provide" read p for "Water-insoluble" read Water-soluble t mation which comprises porous for inser formation in an amount sufficient to contact all Column 2, 1

column 3, line '70, after introducing into said parts of the forma- Signed and sealed this 9th day of June- 1959.

" (SEAL) L Attest:

KARL H AXLINE ROBERT C. WATSON Attesting ()flicer Commissioner of Patents rovides column 3, line 4.5, 

1. THE METHOD OF SEALING A WATER-BEARING, POROUS FORMATION WHICH COMPRISES INTRODUCING INTO SAID FORMATION IN AN AMOUNT SUFFICIENT TO CONTACT ALL PARTS OF THE FORMATION TO BE SEALED, A MIXTURE CONSISTING ESSENTIALLY OF AN AQUEOUS SOLUTION OF A WATER SOLUBLE SALT OF A WATER-INSOLUBLE ORGANIC ACID AND A MATERIAL WHICH HYDROLYZES TO YIELD A FREE ACID SELECTED FROM THE GROUP CONSISTING OF WATER-INSOLUBLE ANHYDRIDES AND WATER-SOLUBLE ALKYL ESTERS OF CARBOXYLIC ACIDS. 